| 摘要 |
<p>NEW MATERIAL:The compound of formula I [R2 and R3 are OH-protecting group; X is (protected) carbonyl or carboxyl; R22 and R23 are H or OH- protecting group; one of R' and R'' is H and the other is methyl or R' and R'' together form methylene]. EXAMPLE:(22R,23R)-2alpha,3alpha,22,23-bisisopropylidenedioxy-24,25-dim ethyl-5alpha- cholestan-6-one. USE:Synthetic intermediate for 25-methylbrassinosteroid. PREPARATION:The objective compound wherein R22 and R23 are H can be produced by (1) reacting an aldehyde compound of formula II with an organoaluminum reagent of formula III, (2) oxidizing the obtained steroid compound of formula IV with a peracid such as m-chloroperbenzoic acid to obtain an epoxy compound of formula V and (3) opening the epoxy ring of the compound with aluminum isopropoxide.</p> |
